text: Hexa(tert-butoxy)ditungsten(III) is a catalyst for alkyne metathesis.  The catalytic cycle involves an carbyne intermediate.
  Some carbyne complexes react with electrophiles at C-carbyne followed by association of the anion.  The net reaction gives a transition metal carbene complex:
  :LM≡CR  +  HX  →   L(X)M=CHR
  These complexes can also undergo photochemical reactions. 
  In some carbyne complexes, coupling of the carbyne ligand to a carbonyl is observed. Protonation of the carbyne carbon and conversion of the carbyne ligand into a π-allyl.